FM-CW radar system

1. An FM-CW radar system which transmits an FM-CW wave and receives a reflected wave from a target object, comprising: modulating signal generating means capable of changing a modulating signal to be applied to said FM-CW wave; calculating means for calculating a distance or relative velocity with respect to said target object by performing processing for detection of said target object by fast-Fourier transforming a beat signal occurring between a transmitted signal of said FM-CW wave and a received signal of said reflected wave; and control means for determining a detection range based on the distance calculated by said calculating means, and for performing control for said modulating signal to be changed by said modulating signal generating means; wherein when two or more target objects are detected, said control means selects the shortest distance from among the distances of said detected target objects calculated by said calculating means and determines said detection range based on a distance obtained by adding a prescribed distance to said selected distance.

2. An FM-CW radar system as claimed in claim 1 , wherein said modulating signal generating means is capable of changing said modulating signal by changing one parameter selected from among a modulation frequency, a triangular wave frequency, and a transmit wave center frequency associated with said FM-CW wave.

3. An FM-CW radar system which transmits an FM-CW wave and receives a reflected wave from a target object, comprising: modulating signal generating means capable of changing a modulating signal to be applied to said FM-CW wave; calculating means for calculating a distance or relative velocity with respect to said target object by performing processing for detection of said target object by fast-Fourier transforming a beat signal occurring between a transmitted signal of said FM-CW wave and a received signal of said reflected wave; and control means for determining a detection range based on the distance calculated by said calculating means, and for performing control for said modulating signal to be changed by said modulating signal generating means; when a vehicle equipped with said radar system is traveling around a curve, and when a detected target object can be judged to be a fixed object, said control means performs control to change said modulating signal so that said detection range becomes equal to a distance obtained by subtracting a prescribed distance from the distance of said target object calculated by said calculating means.

4. An FM-CW radar system as claimed in claim 1 or 3 , wherein said FM-CW wave is transmitted as a plurality of beams over a prescribed scanning angle, and said modulating signal for changing said detection range is changed for each of said beams.

5. An FM-CW radar system as claimed in claim 3 , wherein said modulating signal generating mean is capable of changing said modulating signal by changing one parameter selected from among a modulation frequency, a triangular wave frequency, and a transmit wave center frequency associated with said FM-CW wave.